Detective exaggerated over the same thing (5)
I believe the answer is:
ditto
'the same thing' is the definition.
(the thing previously mentioned in a list)
'detective exaggerated over' is the wordplay.
'detective' becomes 'di' (Detective Inspector abbreviation).
'exaggerated' becomes 'OTT' (short for 'over the top').
'over' shows that the letters should be reversed in order.
'ott' back-to-front is 'tto'.
'di'+'tto'='DITTO'
(Other definitions for ditto that I've seen before include "Two dots say same again" , "Duplicate" , "In lists, the same again with two small marks" , "Repeat the word(s) above" , "Dot it for the same again" .)